This application is based upon and claims benefit of priority of Japanese Patent Applications No. 2001-331003 filed on Oct. 29, 2001 and No. 2002-266805 filed on Sep. 12, 2002, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a rotary pump such as a trochoid pump for pressurizing fluid therein, and to a braking apparatus for use in an automotive vehicle in which the rotary pump is used.
2. Description of Related Art
A rotary pump such as a trochoid pump having contacting gear teeth is composed of an inner rotor having outer teeth formed on its outer periphery, an outer rotor having inner teeth formed on its inner periphery, and a casing for containing the inner rotor and the outer rotor therein. The inner rotor and the outer rotor are disposed in the casing so that the outer teeth and the inner teeth engage with each other to form tooth spaces therebetween. The casing is composed of a pair of side plates covering axial surfaces of the inner rotor and the outer rotor, and a center plate covering a radial outer periphery of the outer rotor.
A rotational center of the outer rotor is positioned in a eccentric relation to a rotational center of the inner rotor. The tooth spaces communicating with an inlet port from which fluid is sucked are formed at one side of a centerline connecting both rotational centers. The tooth spaces communicating with an outlet port from which compressed fluid is discharged are formed at the other side of the centerline. The outlet port and the inlet port are formed in the casing. The inner rotor is rotated by a driving shaft connected thereto, and the outer rotor is rotated in the same direction by engagement of the outer teeth of the inner rotor with the inner teeth of the outer rotor. The tooth spaces formed between the outer teeth and the inner teeth vary according to rotation of both rotors, and thereby the fluid such as a braking fluid is sucked into the tooth spaces communicating with the inlet port and pressurized fluid is discharged from the tooth spaces communicating with the outlet port.
Since the inner rotor and the outer rotor rotate in the casing, pumping efficiency is adversely affected if friction between the axial surfaces of both rotors and the casing is high. Therefore, small spaces are provided between the axial surfaces of the rotors and the casing. That is, a thickness of rotors in their axial direction is made a little smaller than an axial height of the inner space of the casing. For this purpose, a thickness of the center plate is made a litter larger than the thickness of both rotors. An example of the rotary pump is shown in JP-A-2000-355274.
In the rotary pump disclosed in JP-A-2000-355274, a side seal 100 is disposed on an axial surface of the inner rotor and the outer rotor. The side seal 100 is provided to divide the inner space between the axial surface of the rotors and the casing into a low pressure space and a high pressure space. For this purpose, the side seal 100 is disposed to fully cover axial ends of a pair of peripheral seals 80 and 81 which seal a circular gap between an outer periphery of the outer rotor and an inner periphery of the casing. That is, the side seal 100 fully covers both sidewalls of each radial groove 73d, 73e in which the peripheral seal is disposed.
A relevant portion of the sealing structure in the rotary pump disclosed in JP-A-2000-355274 is shown in FIG. 11 attached to this application. A portion where a height difference exists between a seal member 80b (including a center plate 73) and an outer rotor 51 is sealed by the side seal 100. However, since the side seal 100 covers both sidewalls of the radial groove 73d, 73e and is supported by both sidewalls, the side seal 100 is not easily bent in the axial direction. Accordingly, a large gap 99 is formed between the side seal 100 and the outer rotor 51 as shown in FIG. 11. The fluid in the high pressure space flows into the low pressure space through the large gap 99, and therefore sealing between the low pressure space and the high pressure space becomes insufficient, resulting in decrease of the pump efficiency.
The present invention has been made in view of the above-mentioned problem, and an object of the present is to provide an improved rotary pump in which a side seal disposed on an axial surface of an inner rotor and an outer rotor performs a good sealing function. Another object of the present invention is to provide a braking apparatus in which the improved rotary pump is used.
A rotary pump such as a trochoid pump is composed of an inner rotor and an outer rotor, and a housing for enclosing both rotors therein. The inner rotor has outer teeth engaging with inner teeth of the outer rotor, and both rotors are rotatably housed in a rotor chamber formed in the housing. The outer rotor disposed in the rotor chamber in a eccentric relation to the inner rotor is rotated according to rotation of the inner rotor which is rotated by a driving shaft connected thereto. Capacities in plural tooth spaces formed between the outer teeth and the inner teeth change according to the rotation of both rotors.
The housing includes an inlet port through which fluid such as brake fluid is introduced and an outlet port through which the pressurized fluid is discharged. A pair of peripheral seals and a side seal are disposed in the housing to separate the rotor chamber into a low pressure space communicating with the inlet port and a high pressure space communicating with the outlet port.
The pair of the peripheral seals are disposed in radial grooves formed on an inner periphery of the housing to seal a circular gap between the inner periphery of the housing and an outer periphery of the outer rotor. The pair of peripheral seals slidably contact the outer periphery of the outer rotor and divide the circular gap into the low pressure space and the high pressure space. A part of the circular gap confined between the pair of peripheral seals constitutes a part of the lower pressure space communicating with the inlet port. The other part of the circular gap constitutes a part of the high pressure space communicating with the outlet port.
The side seal is disposed in an axial space formed between an axial surface of both rotors and an axial surface of the housing to divide the axial space into the low pressure space and the high pressure space. The side seal is ring-shaped and disposed in an annular groove formed on the axial surface of the housing facing the axial surface of the rotors. The side seal covers at least both axial ends of the peripheral seals, a tooth space forming a first closure portion, and a tooth space forming a second closure portion. Communication between closure portions and both of the inlet and outlet ports is interrupted. A ring-shaped rubber member may be disposed in the annular groove to push the side seal toward the axial surface of the rotors and to thereby establish a closer contact between the side seal and the axial surface of the rotors. A pair of side seals may be used to seal the axial spaces formed at both sides of the rotors.
The side seal covering the axial ends of the peripheral seals is disposed not to cover sidewalls of the radial grooves belonging to the high pressure space. In other words, the side seal is disposed not to be supported by the sidewalls belonging to the high pressure space. Accordingly, the side seal is easily bent by the high pressure communicating with the outlet port, and thereby the side seal closely contacts the axial surface of the rotors to establish a close sealing. The low pressure space and the high pressure space in the rotary pump are effectively separated from each other by the side seal formed and disposed according to the present invention, and thereby efficiency of the rotary pump is increased.
The rotary pump according to the present invention may be used in a braking apparatus for an automotive vehicle. The rotary pump generates a brake fluid pressure in wheel cylinders, which is hither than the pressure generated according to a brake pedal operation by a driver.
Other objects and features of the present invention will become more readily apparent from a better understanding of the preferred embodiment described below with reference to the following drawings.